Device for the transmission of sound from rooms having a high noise level



June 10, 1958 T. w. E. JILSKI ET AL 2,838,127

DEVICE FOR THE TRANSMISSION OF SOUND FROM R00 VEL MS HAVING A HIGH NO LE Filed Nov. 4, l9

.I I /-r I m y y g H H 3 1 I PE W 9' ra 77 4 DEVICE FGR THE TRANSMISSION OF SOUND FRGM ROOMS HAVING A HIGH NOISE LEVEL Theodor Wilhelm Ernst Jilslsi, Hamburg, Schnelsen, and Otto Gskar iiiegfried Denkhaus, Hamburg, Germany, assignors, by mesne assignments, to North American Philips Company, lino, New York, N. Y., a corporationof Delaware Application November 4, 1953, Serial No. 390,187

4 Claims. (Cl. 131 -27) The present invention relates to a device for the transmission of sound from rooms having a high noise level. More particularly, the invention relates to devices for the transmission of sound from rooms having a very high noise level, such as engine rooms, workshops and the like with the use of amicrophone equipped with a speaking funnel. As a rule, a sound-tight cabin was required hitherto for the acoustic communication to or from noisy rooms, for example a ships engine room. However, such a cabin cannot be provided in many cases due to'lack of space and furthermore it is necessary each time to seek the cabin for listening and speaking and this renders operation difiicult and is troublesome.

It has been found that it is possible to a sufiicient ex tent and without further expedients to provide such engine rooms with sound by the utilization of suitable funnel loud-speakers and the like in conjunction with corresponding amplifying devices. However, in order to bring about also a transmission of speech from the same space, it is impossible to utilize an ordinary microphone, the high noise level making the speech audible with too much ditficulty.

Since there is an urgent need for such speaking devices, efliorts have previously been made in the transmission of speech from an engine room to utilize such a microphone with a speaking funnel and to reduce the interfering noise in such manner that the speaker closes the speaking funnel as much as possible with his mouth. However, it has then been found that ones own voice is not audible as a result of the prevailing noise and that one involuntarily speaks into the microphone with as loud and as high pitched a voice as possible, This results in distortion by the acoustic waves reaching the diaphragm directly, the speech being unnatural and audible with difiiculty only. Furthermore, the diaphragm of the microphone acted as the piston of a pump, since the system comprising the diaphragm, speaking funnel and mouth constituted a closed hollow space, so that static pressure waves also became manifest to a considerable extent. The diaphragm of the microphone thus exhibited amplitudes which were distorted and much too large.

In order to mitigate the said disadvantage, and in accordance with the present invention, an acoustic threshold device by which large amplitudes are damped considerably, but small amplitudes are damped very slightly only is positioned in the path of the acoustic waves. In practice, very satisfactory audibility has thus been found possible, even in noisy rooms. On the one hand, interfering sounds are substantially inaudible by the provision of a mouth-piece and, on the other hand, the audibility is not detrimentally affected by undue sound intensity during speaking. Furthermore, it sufiices if the speaker stands about 1 to 3 crns. away from the mouth-piece, the static pressure waves thus also being avoided. Consequently, an important decrease in noise level and satisfactory audibility are obtained with low, ordinary and hard speech.

A device according to the invention may preferably tes Patent be "so constructed that the threshold device comprises an additional diaphragm of small size which is rigidly secured and which is preferably provided on the inner side of the speaking funnel directly in front of the microphone. Due to the comparatively small surface of the additional diaphragm and the rigid securing thereof, great amplitudes, as shown by experience, are reduced as much as possible, bnt small amplitudes are reproduced with low damping only so as to obtain the desired limitation or formation of the threshold value.

-A device according to the invention may alternatively be so designed that the speaking funnel comprises at least one channel or vent provided at its deepest point. The vent or channel connects the interior of the speakingfunnel in front of the threshold device with the atmosphere and permits levelling of pressure and discharge of condensate. The above-mentioned disadvantage that static pressure waves may also act upon the diaphragm is thus avoided. It will be evident that condensate may readily occur within the speaking funnel due to the water vapor content of the speakers breath and accumulation of such condensate is thus avoided.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, wherein the single figure is a schematic diagram of an embodiment of the device of the present invention.

The device according to the invention comprises a pressure type microphone l screwed on the threaded extremity of a speaking funnel 2. A housing 3 with a cover 4 encloses the microphone 1, which is secured in the cover 4 by screwing the speaking funnel into a centric nave 5 which is internally threaded.

The threshold device in this embodiment comprises an additional diaphragm 8 which is secured by means of a spacer 6 in front of a metal grid 7 inside the extremity of the speaking funnel 2. The securing is efiected in that the corresponding bore of the inlet of the pressure type microphone is urged against the spacer, the metal grid and the additional diaphragm when the microphone is screwed on the speaking funnel. It has been found that excellent results may be obtained with such a device if the additional diaphragm 8 is constituted by a Celluloid disc of 0.5 mm. thickness.

For levelling the pressure and for the discharge of condensate, if any, the speaking funnel 2 exhibits at its deepest point a bore vent, or channel, 9 which connects the interior of the speaking funnel with the atmosphere.

While the invention has been described by means of a specific example and in a specific embodiment, we do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

l. A device for the transmission or sound from rooms having a very high noise level, said device comprising a microphone, a speaking funnel attached at one end to said microphone to direct acoustic waves through said funnel to said microphone, and an acoustic threshold device disposed in the path of the acoustic waves within said funnel, said threshold device comprising an auxiliary diaphragm rigidly secured to said funnel at substantially said one end, said diaphragm having a surface area having dimensions at which acoustic waves having large amplitudes are greatly damped and acoustic waves having small amplitudes are only very slightly damped.

2. A device for the transmission of sound from an area having a very high noise level, comprising a microphone, a speaking funnel having a relatively wide month end and a relatively narrow end, means for attaching said funnel at said narrow end to said microphone to direct acoustic waves through said funnel to said microphone, and an acoustic threshold device positioned in the path of the acoustic waves within said funnel, said acoustic device comprising an auxiliary diaphragm rigidly secured to said funnel at substantially said narrow end in close operative proximity with said microphone, said diaphragm having a surface area having dimensions at which acoustic waves having large amplitudes are greatly damped and acoustic waves having small amplitudes are only very slightly damped.

3. A device for the transmission of sound from an area having a very high noise level, Comprising a microphone, a speaking funnel having a relatively wide month end and a relatively narrow end, means for attaching said funnel at said narrow end to said microphone to direct acoustic waves through said funnel to said microphone, and an acoustic threshold device positioned in the path of the acoustic waves within said funnel, said acoustic device comprising an auxiliary diaphragm rigidly secured to said funnel at substantially said narrow end in substantial contact with said microphone, said diaphragm having a surface area having dimensions at which acoustic waves having large amplitudes are greatly damped and acoustic waves having small amplitudes are only very slightly damped.

4. A device for the transmission of sound from an area having a very high noise level, comprising a microphone, a speaking funnel having a relatively wide month end and a relatively narrow end, means for attaching said 4 funnel at said narrow end to said microphone to direct acoustic waves through said funnel to said microphone, an acoustic threshold device positioned in the path of the acoustic waves within said funnel, said acoustic device comprising an auxiliary diaphragm rigidly secured to said funnel at substantially said narrow end in close operative proximity with said microphone, said diaphragm having a surface area having dimensions at which acoustic waves having large amplitudes are greatly damped and acoustic waves having small amplitudes are only very slightly damped, and a vent connecting the interior of said funnel with the atmosphere, said vent being positioned between said threshold device and said wide end of said tunnel to permit leveling of pressure and discharge of condensate.

References Cited in the file of this patent UNITED STATES PATENTS 829,849 Cutmore Aug. 28, 1906 876,035 Young Jan. 7, 1908 1,606,967 Sprague Nov. 16, 1926 1,757,463 McCann May 6, 1930 2,003,284 Clement June 4, 1935 2,325,688 Landis Aug. 3, 1943 2,627,932 Volkmann et al. Feb. 10, 1953 2,774,438 Bauer Dec. 18, 1956 FOREIGN PATENTS 425,558 Great Britain Mar. 18, 1935 UNITED STATES PAT CERTIFICATE OF CORRECTION Patent No. 2,838,127

' June 10, 1958 Theodor Wilhelm Ernst Jilski et al.

In the heading to the printed .10, insert the followin specification, g:

between lines 9 and Signed and sealed this 7th day of October 1958.

Attest: KARL H, AXLINE ROBERT C. WATSON Attesting Officer Comnissioner of Patents ITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,838,127, T June 10, 1958 Theodor Wilhelm Ernst Jilski -et al.

In the heading to th e printed specification, .lO, insert the following;

between lines 9 and Claims priority, application Germany November 7, 1952 Signed and sealed this 7th day of October 1958.

(SEAL) Attest: KARL H. AXLINE Commissioner of Patents 

